The Science of the Uinta Basin

The Rocky Mountain Basins

The Rocky Mountain intermontane basins are famous for their gorgeous exposures and incredible fossil record, particularly for those deposits that record the Tertiary period.  During the early Tertiary, the Eocene (55-34 Ma) is characterized by the appearance of the modern orders of mammals appearing in the fossil record (carnivores, primates, rodents, lagomorphs [rabbits], bats, artiodactyls [sheep, cows, antelope], and perissodactyls [horses, tapirs, rhinoceroses]). The early Eocene is well-represented in the Rocky Mountain basins of Wyoming, the later Eocene deposits are more common on the high plains (Nebraska, the Dakotas), and the middle Eocene has been found in spotty areas of Oregon, southern California, and southwest Texas. 

 
Map of those Rocky Mountain intermontane basins with Eocene exposures. Map from Gazin 1962, which was adapted from Osborn 1929. The numbers refer to early Eocene localities described in Gazin 1962.

Map of those Rocky Mountain intermontane basins with Eocene exposures. Map from Gazin 1962, which was adapted from Osborn 1929. The numbers refer to early Eocene localities described in Gazin 1962.

The Eocene Epoch

The Eocene epoch spans approximately 55 to 34 million years ago. The early Eocene has been well-studied and early Eocene deposits continue to produce incredible fossils and data about past environments. By comparison, there is much less known about the middle Eocene, particularly the time periods known as the Uintan and Duchesnean North American Land Mammal Ages (NALMAs). Biochronology uses fossils to correlate time and land mammal age is an interval of time that is defined by a group of animals unique to that time period. Land Mammal Ages are used to define time spans in the Cenozoic Era.

We will be using paleomagnetism and detrital zircons to correlate our stratigraphic section in the Uinta Basin with the geomagnetic polarity timescale and to refine where the MECO event occurs in the Uinta Basin.

 
On the left, is the geomagnetic polarity timescale (GMPTS) ranging from the end Cretaceous to the Pleistocene, with epochs divided into European land mammal ages. On the right, is the North American Eocene showing the divisions of the land mammal ages of this continents. The middle Eocene includes the Bridgerian, Uintan, and Duchesnean North American Land Mammal Ages (NALMAs).

On the left, is the geomagnetic polarity timescale (GMPTS) ranging from the end Cretaceous to the Pleistocene, with epochs divided into European land mammal ages. On the right, is the North American Eocene showing the divisions of the land mammal ages of this continents. The middle Eocene includes the Bridgerian, Uintan, and Duchesnean North American Land Mammal Ages (NALMAs).